The amount of wireless communications by a portable or mobile terminal is increasing explosively by the propagation of smart phones. From now on, the form of the communication performed between apparatuses, not via a person, is also assumed as wireless communication. For this reason, the traffic amount of wireless communications may increase by 1,000-10,000 times in and after 2020, compared with the present. Therefore, research of a new communication system is actively underway. Manufacturers developing a radiotelephone system have previously focused their efforts to further improve the frequency usage efficiency of the radiotelephone system, rather than in the Long Term Evolution (LTE) and LTE-Advanced (LTE-A) communication systems of with which the business is done now. One of the leading techniques is a massive multiple-input and multiple-output (MIMO) communication system, which is generally a base station equipped with about one hundred antennas, and communicates with about ten sets of mobile terminals simultaneously.
In a massive MIMO communication system, the frequency usage efficiency can be maintained stably, without receiving most of the noise of a communication channel or the influence of early fading fluctuation. Moreover, in a massive MIMO communication system, channel capacity increases greatly compared with a conventional MIMO communication system. Therefore, the massive MIMO communication system is leading as a next-generation new technology.